Unit Plan 18 (Grade 8 Science): Forces & Motion—Quarter Synthesis

Focus: Explain and model interactions among gravity, electromagnetism, and applied forces using investigations, data, and engineering design solutions.

Grade Level: 8

Subject Area: Science (Physical Science • Forces & Interactions • Engineering Design)

Total Unit Duration: 5 sessions (one week), 50–60 minutes per session

I. Introduction

This synthesis unit pulls together everything students have learned about forces and motion so far. Students revisit gravity, electric and magnetic forces, Newton’s Laws, and engineering design to build a unified model of how different forces interact in real systems. Through stations, mini-investigations, and a capstone “Forces in a System” design challenge, they show how gravitational, electric, magnetic, and contact forces (normal, friction, applied) can combine to control motion. By the end of the week, students can explain and model how multiple forces act together and use data and design criteria to justify engineering choices.

Essential Questions

• How do gravity, electric forces, and magnetic forces compare with everyday contact forces like pushes, normal force, and friction?
• How can we use Newton’s Third Law and net force ideas to explain what happens when objects collide or interact?
• What evidence shows that gravitational interactions are always attractive and depend on mass?
• What data patterns show how electric and magnetic forces depend on factors like distance, charge, and current?
• How can we use engineering design (criteria, constraints, testing, and evaluation) to solve a problem involving multiple types of forces?

II. Objectives and Standards

Learning Objectives — Students will be able to:

1. Identify and compare gravity, electric forces, magnetic forces, and contact forces (normal, friction, applied) in real scenarios, using force diagrams and net force reasoning.
2. Apply Newton’s Third Law to describe action–reaction pairs in collisions and other interactions and to explain features of a design solution (MS-PS2-1).
3. Use or extend data from prior investigations to explain how change in motion depends on the sum of forces and mass (MS-PS2-2).
4. Ask targeted questions about data to determine factors that affect the strength of electric and magnetic forces, and use them to refine models (MS-PS2-3).
5. Construct and present arguments using evidence that gravitational interactions are attractive and depend on mass, at both Earth and planetary scales (MS-PS2-4).
6. Conduct or analyze an investigation showing that electric currents produce magnetic fields, connecting results to electromagnet applications (MS-PS2-5).
7. Define criteria and constraints for a forces-based design problem, develop competing solutions, evaluate them using data, and recommend improvements (MS-ETS1-1, MS-ETS1-2, MS-ETS1-3).
8. Synthesize their understanding in a Forces & Motion Portfolio that includes models, graphs, arguments, and an engineering justification.

Standards Alignment — 8th Grade (NGSS-based custom)

• MS-PS2-1 — Apply Newton’s Third Law to design a solution involving the motion of two interacting objects (e.g., collision buffers, launch/catch systems).
• MS-PS2-2 — Plan or interpret an investigation that shows how net force and mass affect changes in motion (e.g., carts on ramps, different masses/forces).
• MS-PS2-3 — Ask questions about data to determine factors affecting electric and magnetic force strength (e.g., distance, charge, current, orientation).
• MS-PS2-4 — Construct and present arguments that gravitational interactions are attractive and depend on mass (e.g., Earth–Moon, two masses).
• MS-PS2-5 — Conduct an investigation showing that electric currents can produce magnetic fields (e.g., electromagnets, wire + compass).
• MS-ETS1-1 — Define criteria and constraints precisely for a forces-based design problem.
• MS-ETS1-2 — Evaluate competing design solutions with a systematic process.
• MS-ETS1-3 — Analyze test data to determine differences among solutions and identify the best characteristics for improvement.

Success Criteria — Student Language

• I can draw and explain how gravity, electric forces, magnetic forces, and contact forces act on objects in a system.
• I can use Newton’s Third Law to name the action and reaction forces between two interacting objects.
• I can use data and graphs from investigations to explain how the net force and mass changed an object’s motion.
• I can ask and answer specific questions about what affects electric and magnetic force strength.
• I can argue, with evidence, that gravity is always attractive and depends on mass.
• I can explain how electric currents create magnetic fields, using evidence from an electromagnet or wire–compass investigation.
• I can define criteria and constraints, evaluate multiple designs using data, and recommend a solution that best meets the goals.